Recently, liquid crystal display devices have been widely used in liquid crystal panels for liquid crystal TVs or PCs, mobile phones, digital cameras, etc. Conventionally, a liquid crystal display device is provided with a liquid crystal panel member having polarizing plates on both sides of a liquid crystal cell and enables a display by controlling light from a backlight member by the liquid crystal panel member. In this case, the polarizing plate is provided with a polarizer and protective films on both sides of the polarizer. A conventional polarizer is obtained by dyeing a stretched polyvinyl alcohol (PVA) film with iodine or a dichroic pigment, and as a protective film, a cellulose ester film or the like has been used.
Recent liquid crystal display devices have been diversified in use thanks to high quality, and the requirements for durability have become stricter. For example, for outdoor use, it is required to maintain stability in response to an environmental change. As for an optical film, such as the above-described protective film for a polarizing plate used in a liquid crystal display device or an optical compensation film, it is also required to prevent dimensional or optical characteristics from changing in response to a change in temperature or moisture.
Since liquid crystal displays have been made to be used under more harsh conditions, such as outdoor uses, as well as conventional indoor uses, the performance of moisture impermeability in an optical film provided at the outermost surface of a liquid crystal display device has become more important. Also, when used in TVs, which have recently become bigger, this performance may be affected by a trend in which the glass of the liquid crystal cell tends to become thinner. Thus, there are concerns for the tendency of warpage increase and the influence on light leakage occurring over time under a high-temperature high-humidity condition.
Patent Document 1 discloses an optical film, in which a large quantity of acrylic resin, such as polymethyl methacrylate (PMMA), is added to cellulose ester, in order to provide an optical film having a high transparency, a low moisture absorbability, a high thermal resistance and a high mechanical strength.
Also, a film provided with a coating layer on a base film has also been known. For example, Patent Document 2 discloses a film in which on a cellulose acylate base film having a film thickness of 80 μm, a coating layer formed of a composition containing a compound having a cycloaliphatic hydrocarbon group and two or more ethylenically unsaturated double bonds in a molecule.